Emerging alternative energy sources, although offering a promising future, suffer from unstable input sources. To resolve this problem DC-DC converters may be used as a stabilizing circuit; and, in the case of a well-known boosting topology, a low varying input voltage can be boosted to provide a stable output voltage capable of delivering required potential for a multitude of applications. Typically, such a circuit is a LC circuit, including an inductor and a switch responsible for the voltage boost, as well as a rectifying device and a ripple minimizing capacitor. The gain of the overall circuit is strictly dependent on the nature of the waveform fed to the switch—i.e. a transistor. Two approaches in particular are available: fixed-frequency/varying pulse-width or pulse-width modulation (PWM) converters, and varying-frequency/fixed pulse-width or resonant converters.
PWM converters dominate the market primarily due to their circuit simplicity and ability to offer a voltage gain greater than unity. More specifically, the voltage gain is provided by the boost converter topology. The most common method of dictating the switching behaviour of the boosting circuit's transistor is through n extrinsic source, usually in form of a digital microcontroller (MCU). The incompatibility between a digitally driven switch and the use of circuits operational at higher frequencies lies in the latter's objective to minimize both the area employed by the circuit and its bulk costs. To further elaborate, if localized boosting is required for an unstable input source, the digital approach is rendered unfeasible given the size needed for the MCU.
The need for an extrinsic source for the transistor is eliminated in a resonant converter in which the LC network causing the self-oscillation at resonance is implemented within the circuit, which in turn determines the switching behaviour. The resonant converter is also operable at higher frequencies which allows for the miniaturization of component sizes, making it ideal for integrated circuit applications. Unfortunately, this class of converters poses the gain limitation of at most unity, which is achieved only at resonance.
FIG. 1 displays a circuit schematic of a typical prior art self-oscillating boost converter which adopts a single frequency and a single duty which contains no mechanism for regulation. The circuit includes components such as inductor (L1); rectifying diode (D1); and ripple-free capacitor (C2). The output terminal (TOUT) is taken at the positive terminal (5) of capacitor (C2). The self-oscillating network includes capacitor (C1) and resistor (R1) in parallel with their low-terminal (4) connected to oscillating bipolar junction transistor Q2. The circuit also includes input terminal (TIN).